Band gap and work function characterization of back-gated 2D TMDCs using KPFM

In this work, Kelvin probe force microscopy (KPFM) is used to visualize the electronic band alignment of 2D van der Waals heterostructures. By quantitatively mapping the work function and bandgap, KPFM reveals the suitability of transition metal dichalcogenides for novel heterojunction devices. A bulk PtSe₂/few-layer MoS₂ heterojunction was fabricated and imaged using KPFM. The resulting surface potential characteristics of monolayer and trilayer MoS₂ was described by an electrostatic model yielding band gaps in alignment with previously reported values. Using this model, the Fermi level position within the bandgap and corresponding work function was accurately characterized for several 2D TMDCs. Furthermore, the electrical behavior of the heterojunction was compared to two monolayer WSe₂ field-effect transistors with multilayer graphene contacts.